/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */

class Solution {
public:
    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
        if(root==nullptr){return root;}
        if(p->val<=root->val && root->val<=q->val){return root;}
        else if(p->val<root->val && q->val<root->val){root=lowestCommonAncestor(root->left,p,q);}
        else if(p->val>root->val && q->val>root->val){root=lowestCommonAncestor(root->right,p,q);}
        return root;
    }
};